The present invention relates generally to light emitting diodes (LEDs), and specifically to an LED lamp apparatus that includes an LED as a light source for use in spot lighting illuminations in environments such as in the interior of a motor vehicle.
LED lamps are becoming a more popular choice than conventional bulb lamps for use in many conventional illumination applications. This is because an LED lamp is suitable for use as a light source in spot light illumination because of its characteristic of being highly directional. This directional characteristic of the LED lamp is primarily controlled by a lens and/or a cover that changes a portion of the LED illumination.
The directional characteristic of an LED lamp is suitable for obtaining a narrow illumination area. However, because the directional characteristic creates a distinct boundary between the illuminated area and the peripheral area (non-illuminated area), the LED lamp is not preferable for all applications. For example, for the purpose of both improving visibility and creating a relaxing atmosphere (or luxury atmosphere) in the vehicle interior, it is preferable to use an illumination pattern in which the peripheral area of the illumination area is gradated.
On the other hand, an LED lamp can be designed to emit light having a color that differs from the original color of the light emitted from the LED. This can be accomplished through the use of fluorescent particles, which are excited by light emitted from the LED, in the LED lens or in another location in proximity to the lens. In one version of this type of LED lamp, a white LED lamp may include a blue LED and a lens with yellow or greenish yellow fluorescent particles. By mixing the blue light emitted by the LED and the yellow or greenish yellow light output through the fluorescent particles, the white LED lamp can emit a white light. However, because of the difference of the emitting points between the blue light (the position of the LED) and the yellow or greenish yellow light (the position of the fluorescent materials), mixing the colors of these two sources thoroughly over the entire area being illuminated is difficult. As a result, yellowish light is observed around the peripheral area of the illuminated area, thereby resulting in non-uniform color illumination.
Other LED lamps have been designed to exhibit uniform color illumination. However, such LED lamps typically exhibit non-uniform degrees of brightness.